Normal Rogue Subclass

This subclass is a unique Charisma based option for the rogue that not only focusses on the situational aspect of copying other creatures' Skills or Saving throws but allows you to use Charisma in replacement of Dexterity for finesse weapons. It's features allow you to add proficiencies, expertise, or advantage on Skills and Saving throws which last for the day, doing so in combat benefits you and grants the ability to make enemies have harder times on rolls. This subclass relies heavily on line of sight of targets, enemies attempting saving throws, and unlocking your level 9 feature Hyper Aware to both increase your copycat opportunities and test your ability to pay attention and roleplay through combats. 

Memory Slots

When you choose this subclass at 3rd level, you gain a new resource named "Memory Slots." Starting at 3rd level you have 2 Memory Slots and gain more at levels 9, 13, and 17. Your Memory Slots are always reset on a long rest, but when taking a short rest you are instead given the option to reset up to half your total Memory Slots (rounded down with a minimum of 1) or keeping the Memory Slots currently in use. 

Copycat

You may expend a Memory Slot to copy an Extraordinary Skill or Extraordinary Act that has been performed by another creature you could see within the last 6 seconds (1 round). When you choose to do so and the creature is not the same or lower Level/CR than your rogue level, you must succeed a Performance Check with a DC of 10+ the creature's Level/CR in order to successfully copy the skill or act. If you fail then you are unable to attempt copying the same Skill or Act unless the creature rolls again. 

When you copy a creature you are currently in combat with, you not only copy the Skill or Act but as long as you can see them they have disadvantage when doing future rolls of the specific copied Skill or Act.

Extraordinary Skill: Copy a successful skill check. As long as you are aware of what skill it was then you can expend an available Memory Slot to temporarily gain proficiency with that skill. If you already have proficiency with said skill then you gain expertise and if you already have expertise you gain advantage. These effects last until the correlated Memory Slot is reset. (You cannot copy more than 1 of the same skill at a time) 

Extraordinary Act: Copy a successful saving throw. As long as you are aware of which saving throw was used then you can expend an available Memory Slot to temporarily gain proficiency with that saving throw. If you already have proficiency with that saving throw then you gain expertise and if you already have expertise then you gain advantage. This effect lasts until you fail that saving throw or the Memory Slot is reset. (You cannot copy more than 1 of the same saving throw at a time) 

NOTE: Make sure to keep track of which creatures you copy as it is a vital mechanic in combat.

Mirrored Movement

When you choose this subclass at 3rd level, you gain the ability to perform the attacks and movements in mimic of others. Your movements become more of a performance as you mirror the creature you are fighting, allowing finesse weapons to now scale with Charisma instead of Dexterity when you wield them (you will need to manually change this). When dealing damage this way while you are currently copying your target with the Copycat feature, then you can add your sneak attack damage to the roll even if you don't have advantage but only as long as you don't have disadvantage. 

Additionally, when a grounded (Non flying or levitating) creature within 5ft moves away from you on their turn without dashing, you can use your reaction and force them to roll Dexterity Saving Throw DC: [10 + Charisma Modifier + Proficiency], on a fail you momentarily prevent the creature from traveling farther than your max Walking Speed and follow the creature, staying within 5ft the whole time. When successfully doing this, you perfectly mimic the creature you are following and this movement does not provoke opportunity attacks. If the creature succeeds the saving throw it moves as normal and you stay when you are.

Hyper Awareness

Starting at 9th level you gain the ability to catch even the smallest hint that someone is up to something. You are automatically aware of any skill check or saving throw rolled by a creature weaker than you that you have the ability to see withing 60ft. Additionally, you gain proficiency with Investigation checks and Perception checks, if you are already proficient with one or both of these then you may choose other skills.

While viewing a creature, you can use your bonus action to force them to roll a Charisma Saving Throw DC: [10 + Charisma Modifier + Proficiency] to determine if they are on par or stronger than you. When successfully examining a creature this way, you mark the creature and become hyper aware of their movements and actions, you know what skill checks or saving throws they roll for the next minute, given they are within 60ft of you and you have line of sight of them. While doing this in combat, the targeted creature also gains disadvantage on attack rolls against you for the duration as long as they are within range and you are copying them with your Copycat ability.

Once the active version of this feature is used (whether it fails or not), it can't be reactivated on the same creature again until you finish a long rest. 

Weaker: Their Level/CR is lower than your current level.

On Par: Their Level/CR is equal to your current level.

Stronger: Their Level/CR is greater than your current level.

NOTE: You can only use the active feature on one target at a time and recasting this ability on a new creature will cause you to lose the effect against the previous creature.

Copy and Paste

At level 13, you've honed your process of memorizing and then executing skills to the point of perfection. When you fail a saving throw or skill check that you witnessed another creature succeeded within the last minute, you can choose to succeed instead. This feature can only be used once per day.

If this is used on a saving throw or skill that is currently taking up a memory slot with your Copycat feature, then the use of this ability is free and does not exhaust it's daily charge. This part of the feature can be used even when you have already consumed your daily charge. 

Keen Eyes

At 17th level your eyes have been trained to never lose sight of dangers. You have gained a Truesight range of 60ft whenever a creature that is being copied by your Copycat ability is within 60ft of you. Viewing a creature this way counts as them being within your line of sight for the sake of benefitting your previous features.